Erbium-doped yttrium-aluminum-garnet laser crystals (Er:_Y3Al5O12 or Er:YAG) have a great advantage in the wavelength range of 2.94 µm, where the laser beam is strongly absorbed in water and is therefore of interest in medicine. Er:YAG has high optical quality, low scattering losses, high output power and is chemically and mechanically stable. This makes it ideal for hard tissue removal. Er:YAG is a crystal with a large pumping range from 600nm to 800nm. All these properties make Er:YAG ideal for applications in surgery, dentistry and other medical fields.